Method for manufacturing a biplate assembly, a biplate assembly and a bipolar battery

ABSTRACT

The present invention relates to a method for manufacturing a biplate assembly including a biplate, a negative electrode and a positive electrode. The method comprises the steps: selecting the size of the biplate, arranging the positive electrode, which is formed by a compressed first powder, to a first side of the biplate, the first powder containing positive active material, and arranging the negative electrode, which is formed by a compressed second powder, to a carrier arranged within the biplate assembly, the second powder containing negative active material. The carrier is preferably a side opposite to the first side of the biplate. The invention also relates to a biplate assembly and a bipolar battery including at least one biplate assembly.

TECHNICAL FIELD

[0001] The present invention relates to a method for manufacturing a biplate assembly as defined in the preamble of claim 1. The invention also relates to a biplate assembly as defined in the preamble of claim 15, and a bipolar battery made up from at least one biplate assembly as defined in the preamble of claim 25 and claim 29.

BACKGROUND OF THE INVENTION

[0002] Bipolar batteries have been used to improve battery energy storage capacity on a weight and volume basis, to reduce packing weight and volume, to provide stable battery performance and low internal resistance.

[0003] A bipolar battery construction comprises an electrically conductive bipolar layer, so called biplate, that serves as electrical interconnection between adjacent cells in the battery as well as a partition between the cells. In order for the bipolar construction to be successfully utilised, the biplate must be sufficiently conductive to transmit current from cell to cell, chemically stable in the cell's environment, capable of making and maintaining good contact to the electrodes and capable of being electrically insulated and sealable around the boundaries of the cell so as to contain electrolyte in the cell.

[0004] These requirements are more difficult to achieve in rechargeable batteries due to the charging potential that can accelerate corrosion of the biplate and in alkaline batteries due to the creep nature of electrolyte. Achieving the proper combination of these characteristics has proven very difficult. For maintenance-free operation it is desirable to operate rechargeable batteries in a sealed configuration. However, sealed bipolar designs typically utilise flat electrodes and stacked-cell constructions that are structurally poor for containment of gases present and generated during cell operation. In a sealed construction, gases generated during charging then need to be chemically recombined within the cell for stable operation. The pressure-containment requirement creates additional challenges on designing a stable bipolar configuration.

[0005] In a bipolar battery there is, as mentioned above, a need for electrodes that should be in good contact with the biplate. Presently, the negative and positive electrode being in contact with the biplate are manufactured separately and treated in such a way to improve contact with the biplate when attached to it. Such treatments are disclosed in U.S. Pat. No. 5,611,823, by Klein, where the electrodes are manufactured from electrochemically active material prepared by coating non- to low-conductive particles of a metal hydroxide or metal oxide powder with nickel using a electroless nickel coating process.

[0006] Other treatments to manufacture individual robust, positive and negative electrodes is to utilise a current collecting grid for the dual purpose of supporting the electrochemically active materials, and conducting the electric current from the electrode via the conductive grid.

[0007] Pressed powder has previously been used when manufacturing separate electrodes. An article, Ni—MH Battery Electrodes Made by a Dry Powder Process was published in the Journal of the Electrochemical Society, Vol. 142, Number 12, December 1995 and is hereby incorporated by reference.

SUMMARY OF THE INVENTION

[0008] The object of the present invention is to provide a method for manufacturing a biplate assembly having a reduced weight, a reduced size and a maintained or improved battery energy storage capacity compared to prior art.

[0009] This object is achieved by a manufacturing method as defined in the characterising portion of claim 1, the biplate assembly as defined in the characterising portion of claim 15, and a bipolar battery as defined by the characterising portion of claim 25 and 29.

[0010] An advantage with the present invention is that a biplate assembly may be obtained, where each electrode may have a thickness ranging from 0.1-1.0 millimetre, especially for power applications, thus reducing the weight and volume of each biplate assembly and as a result reducing the weight and volume of the complete bipolar battery. For other applications the thickness of each electrode may exceed 1.0 millimetre.

[0011] Another advantage with the present invention is that it is possible to manufacture less costly batteries than present batteries, due to the manufacturing method.

[0012] Another advantage with the present invention is that more uniform electrodes may be created, thereby shortening the current paths within each electrode.

[0013] Still another advantage is that fewer parts are needed to manufacture the biplate assembly, since no grids are required, and no intercell components are required in a bipolar battery. This lowers the manufacturing cost considerably.

[0014] An advantage with an embodiment of the present invention is that the characteristics of the battery, including the electrodes according to the invention, will be improved since an improved efficiency due to better conductive paths between the biplate and the electrodes are achieved when the electrodes are manufactured directly on the biplate.

[0015] Still an advantage with an embodiment of the present invention is that the internal resistance within an electrode is reduced due to providing a three-dimensional roughness on the biplate, the biplate either carrying the electrodes or being arranged adjacent to an electrode when mounted in a bipolar battery.

[0016] A further advantage with an embodiment of the present invention is that the internal resistance within an electrode is further reduced by providing conductive fibres to the positive active material (PAM) and the negative active material (NAM).

[0017] The reduction in internal resistance will cause less heat to be generated, thereby further improving the characteristics of the biplate assembly.

[0018] Further objects and advantages of the present invention will be apparent to those skilled in the art from the following detailed description of the disclosed bipolar electrochemical battery and the methods for producing biplate assemblies having pressed electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1a-1 g shows a manufacturing process of a biplate assembly according to the present invention.

[0020]FIG. 2 shows a cross-sectional view of the biplate assembly along A-A′ in FIG. 1g.

[0021]FIG. 3 shows a cross-sectional view of an alternative biplate assembly along A-A′ in FIG. 1g.

[0022]FIG. 4 shows a flow chart describing a first embodiment of the manufacturing process according to the invention.

[0023]FIG. 5 shows a flow chart describing a second embodiment of the manufacturing process according to the invention.

[0024]FIG. 6 shows a bipolar battery comprising biplate assemblies manufactured according to the present invention.

[0025]FIG. 7 shows a second biplate assembly according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026]FIG. 1a-1 g shows a manufacturing process to obtain a biplate assembly according to the present invention. FIG. 1a shows a biplate 10 having a first side 11 and a second side 12, which size is selected dependent on the application.

[0027] A too large biplate will cause no, or bad, heat transition away from the biplate. An increased temperature will degenerate the capacity of the bipolar battery, where the biplate assembly is mounted, due to that the electrolyte present between two biplate assemblies is tied up to the positive electrode of the biplate assembly causing more heat to generate, and so on. So it is important that the size of the biplate is selected with care to avoid the above described heat transition problem.

[0028]FIG. 1b shows the next step in the manufacturing process where a first limited area 13 is selected on the first side 11 of the biplate 10, where a first electrode is to be formed.

[0029]FIG. 1c shows an optional step in the manufacturing process, where at least the limited area 13, selected in FIG. 1b, is treated in such a way to obtain a three-dimensional roughness 14. This way the surface area, where the first electrode is to be formed, is increased. Furthermore the roughness will also make it easier to keep the electrode in place, since the electrode is mainly made out of a pressed powder.

[0030]FIG. 1d shows the next step where the first electrode 15, e.g. the positive electrode, is created by pressing a first powder compound, containing a Positive Active Material (PAM), onto the first side 11 of the biplate 10.

[0031]FIG. 1e shows the next step where the biplate 10 has been turned up side down, i.e. the positive electrode 15 is facing down and the second side 12 is facing up. A second limited area 16, is selected, which preferably has the same size as and is arranged directly opposite to the first limited area 13.

[0032]FIG. 1f shows another optional step where the same treatment is performed as described in connection with FIG. 1c, obtaining a three-dimensional roughness 17 similar to the one in FIG. 1c.

[0033]FIG. 1g shows the final step in the manufacturing process where a second electrode 18, e.g. the negative electrode, is created by pressing a second powder compound, containing a Negative Active Material, onto the second side 12 of the biplate 10.

[0034] Thus, a complete biplate assembly is made including a biplate, a positive electrode and a negative electrode, which are created by depositing and pressing powder directly onto the biplate. This makes it possible to manufacture very thin electrodes, having a thickness ranging from 0.1 to 1.0 millimetre, preferably in the range 0.25 to 0.5 millimetre. This approach is essential when manufacturing bipolar batteries for power applications. In other applications where it is desirable to extract energy from the battery during a long period of time, e.g. 4-8 hours before recharging, thicker electrodes over 1.0 millimetres are necessary to achieve this.

[0035] Although the possibility to manufacture thin electrodes is a major advantage when it comes to power applications, the invention should not be limited to “thin” electrodes. The invention is suggested to cover any type of electrodes having a PAM and/or NAM which include the process of pressing the active material into electrodes, irrespectively of the thickness of each electrode and the presence of any additional material within the electrodes, such as conductive grids, metal coated fibres, etc.

[0036] The positive electrode has preferably lower capacity than the negative electrode due to the recombination process within a bipolar battery where the biplate assembly will be mounted.

[0037] The manufacturing process, as described above, may naturally perform the illustrated steps in a different order to obtain the same result. As an example, the step for treating the first limited area 13 in FIG. 1c may be followed by the step of treating the second limited area 16 in FIG. 1e, before the positive 15 and negative 18 electrodes are formed on the respective sides 11, 12 of the biplate 10.

[0038]FIG. 2 shows a cross-sectional view of the biplate assembly along A-A′ in FIG. 1g. The biplate assembly 20 comprises the biplate 10, the positive electrode 15 arranged on the first side 11 of the biplate 10 and the negative electrode 18 arranged on the second side 12 of the biplate 10.

[0039] The optional three-dimensional roughness 14, 17, respectively, are also shown in FIG. 2, where the increased surface area under each electrode is illustrated in an exaggerated way. The three-dimensional roughness may be established by using a technique called “flame spraying”, where the surface of the biplate is treated with a material similar to the material of the biplate during a high temperature, e.g. 950-1050° C. Conventional flame spraying uses superheated gasses at high velocity, which produces overlapping layers of thin pancake type structures. The material of the biplate is preferably nickel or nickel plated steel and the biplate is preferably flame sprayed by using nickel fibres to create a three-dimensional surface. In the preferred embodiment, vertical and sloped fibres will be present which will deform when the powder is compacted, and will hold the compacted powder better during the manufacturing process. The technique for flame spraying is well known for a person skilled in the art and is not further elaborated in this disclosure.

[0040] The positive electrode 15 is in this embodiment also provided with nickel fibres 21 to increase the conductivity between the biplate 10 and the positive electrode 15. These nickel fibres 21 may be obtained from INCO (International Nickel Coporation), item 255 or 210.

[0041] By using a blend of active materials and conductive fibres, both for PAM and NAM, the materials may be assembled between the conductive biplates and held in position by assembly pressure. The PAM is typically a nickel hydroxide and the NAM is typically a metal hydride.

[0042]FIG. 3 shows a cross-sectional view of an alternative biplate assembly along A-A′ in FIG. 1g. The alternative biplate assembly 30 comprises the biplate 10, the positive electrode 15 arranged on the first side 11 of the biplate 10 and the negative electrode 18 arranged on the second side 12 of the biplate 10.

[0043] The optional three-dimensional roughness 14, 17, respectively, are also shown in FIG. 3, where the increased surface area under each electrode is illustrated in an exaggerated way. The three-dimensional roughness is in this alternative embodiment created by using an etching technique that remove material from the biplate 10. Several etching techniques may be used to obtain the three-dimensional roughness, such as wet etching and plasma etching. The etching technique is more difficult to implement in the manufacturing process due to the nature of etching and therefore the flame spraying technique is preferred over the etching technique.

[0044] The three-dimensional roughness 14, 17, respectively, in FIG. 2 and 3 only is present under the formed electrodes, but it is of course possible to manufacture a biplate assembly where the electrodes only cover a part of the area having a three-dimensional roughness.

[0045] An alternative method for manufacturing a biplate assembly would be to first perform the steps described in connection with FIG. 1a to 1 d. The result of the manufacturing steps may be seen in FIG. 1d. Instead of turning the biplate up side down as illustrated in FIG. 1e, it is suggested to add a separator containing electrolyte, on top of the first electrode, and thereafter forming a second electrode on top of the separator. The step of selecting a second limited area and the optional step of creating a three-dimensional roughness as illustrated by FIG. 1f, may either be performed before the separator is added to the first electrode or after the second electrode has been formed.

[0046] In addition to the manufacturing method described in connection with FIG. 1a-1 g, it is also possible to produce a biplate assembly having separately manufactured electrodes.

[0047]FIG. 7 shows a second embodiment of a biplate assembly 70 manufactured using the alternative method as discussed in the paragraph above, but instead of pressing the powder directly to the biplate 10, the electrodes are manufactured separately.

[0048] The biplate assembly 70 comprises a biplate 10, a positive electrode 71 arranged to a first side 11 of the biplate 10, a separator 65 arranged on top of and covering the positive electrode 71, and a negative electrode 72 arranged to the separator 65. The thickness of the biplate 10 may be reduced compared to the thickness of the biplate used in connection with the manufacturing method described in FIGS. 1a-1 g, since the biplate does not have to carry the electrodes during manufacture.

[0049] The manufacturing process of an electrode include forming an electrode by compressing a positive active material PAM or negative active material NAM, dependent on if a positive or a negative electrode is to be made, into a flat electrode material. This electrode material is very fragile, but may be handled using for instance vacuum tools.

[0050] It is possible to reduce the fragility by introducing an polymer mesh, preferably an extremely fine polymer mesh, to serve as a support means for the compressed powder. When the support means is present it is possible to manufacture a long continuous strip without generating any sharp edges that would cause shorts, as is the case with existing electrodes using metallic grids. The scrap generated could easily be ground, sifted and reused.

[0051] The use of the polymer mesh makes it possible to create an irregular shaped electrode without generating excessive scrap. The method of manufacture would include the following steps:

[0052] use the support mesh in place of the metallic grid support in the production of a continuous electrode strip,

[0053] punch out the desired electrode shape, and

[0054] grind and recycle the scrap.

[0055] The resulting electrode is thereafter arranged to the biplate 10 or the separator 65 as described above.

[0056] When a bipolar battery, as illustrated by FIG. 6, is taken apart after use it is very difficult to tell which type, of the two different kinds disclosed above, of biplate assembly has been used since the manufacturing principle behind the bipolar battery is to use pressure to hold every part together within the battery.

[0057]FIG. 4 shows a flow chart describing the manufacturing process according to a first embodiment of the invention. The flow starts in step 40 and in step 41 a size of the biplate has to be selected. This may be done in several way, e.g. each biplate may be cut out of a metal sheet having a predetermined thickness. Another way is to feed biplate material into the manufacturing process from a supply of biplate material, having a predetermined width and thickness. The size of each biplate is thereafter selected by cutting the biplate material in a desired length.

[0058] The flow proceeds to step 42 where the first electrode, e.g. the positive electrode, is formed by pressing a first type of powder onto a first side of the biplate. Then, in step 43, the second electrode, e.g. the negative electrode, is formed by pressing a second type of powder onto a second side, opposite to the first side, of the biplate. The flow ends in step 44.

[0059] A complete biplate assembly having a biplate, a positive electrode and a negative electrode has been created, where the electrodes have been formed directly onto the first and second side, respectively, thereby improving the characteristics of the biplate assembly.

[0060] An alternative flow, for manufacturing the alternative biplate assembly is to add a step between step 42 and 43, where a separator is added onto of the first electrode, and step 43 is performed in such a way to create a second electrode on top of the separator.

[0061]FIG. 5 shows a flow chart describing a second embodiment of the manufacturing process according to the invention. The flow starts in step 50 and proceeds to step 51 where the size of the biplate is selected as described in connection with step 41 in FIG. 4. A limited area on a first side of the biplate is thereafter selected in step 52 where the positive electrode is to be formed.

[0062] Thereafter, the flow continues to the optional step 53, where a treatment of the first side, or at least the limited area selected in step 52, is performed. The object of the treatment is to obtain a three-dimensional roughness of at least the area where the positive electrode is to be formed.

[0063] In step 54 the positive electrode is formed by pressing powder, containing PAM, and, optionally, including metal fibres to enhance the conductivity between the positive electrode and the biplate.

[0064] In step 55, the manufacturing process determines if all electrodes have been formed on the biplate assembly. If not the flow returns to step 52 via a step 56, where the biplate is turned up side down so that the second side of the biplate face upwards. Step 52 through 54 is thereafter performed to form the negative electrode.

[0065] If all electrodes have been formed the flow continues to step 57, where the manufacturing process determine if another biplate assembly shall be manufactured. If another biplate shall be manufactured, the flow returns to step 51 and the process is repeated again. If not, the flow continues to step 58 where the process ends.

[0066] The alternative embodiment of the biplate assembly may also be illustrated by using a slightly modified FIG. 5.

[0067] The steps of the alternative method of manufacture, follows the description according to steps 51-55, with the additional feature that if not all electrodes have been formed on the biplate assembly the flow continues to a step where a separator is added on top of the first electrode and back to step 52. Steps 52 and 53 are performed in the same way as mentioned above, but step 54 is replaced by a step where the negative electrode is formed on top of the separator by pressing. The rest of the manufacturing steps are the same.

[0068] In some applications, such as power applications, it is beneficial to have as thin electrodes as possible. A preferred thickness for a power application is between 0.1 to 1.0 millimetre, which may be achieved by the proposed method of manufacture. In other applications, such as long time discharge, it is desired to have electrodes that have a thickness of more than 1.0 millimetre, which may be achieved by the proposed method of manufacture, but also of by combining known methods with the present method.

[0069]FIG. 6 shows a bipolar battery 60 including a housing 61, a biplate assembly 62, a negative end terminal 63, only having a negative electrode 18, and a positive end terminal 64 only having a positive electrode 15. A separator 65 is arranged between the negative end terminal 63 and the positive electrode 15 of the biplate assembly and another separator 65 is arranged between the negative electrode 18 of the biplate assembly and the positive end terminal 64.

[0070] The separator is porous and may hold a certain volume of electrolyte. Typically the separator is in a starved condition, resulting in gas passages that permit gas recombination. The principle of recombination batteries is not further elaborated in this description since it is common knowledge for a person skilled in the art.

[0071] The negative electrode 18 of the negative end terminal 63 together with the separator 65 and the positive electrode 15 of the biplate assembly 62 make up a first cell 66 within the bipolar battery 60. The negative electrode 18 of the bipolar assembly 62 together with the separator 65 and the positive electrode 15 of the positive end terminal 64 make up a second cell 67 within the bipolar battery 60.

[0072] The negative 63 and positive 64 end terminals may naturally be made from the same manufacturing process described above, with the exception that only one side of the biplate has a formed negative 18 or positive 15 electrode, respectively.

[0073] In the case the bipolar battery was made from the alternative biplate assembly, having a biplate with a positive electrode formed on one side, a separator added on top of the first electrode and a negative electrode formed on top of the separator, it would only comprise two biplate assemblies. The first biplate assembly being used as a positive end terminal and making up the second cell 67 in the battery except for the biplate provided by the second biplate assembly. The second biplate assembly makes up the first cell 66 in the battery except for the biplate being used as a negative end terminal. The negative end terminal only comprises a biplate with a three-dimensional roughness on the side where the electrode should make contact. 

1. A method for manufacturing a biplate assembly including a biplate, a first electrode, and a second electrode, said method comprises the steps: selecting the size of the biplate, arranging the first electrode, which is formed by a compressed first powder, to a first side of the biplate, said first powder containing a first type of active material, and arranging the second electrode, which is formed by a compressed second powder, to a carrier arranged within said biplate assembly, said second powder containing a second type of active material, opposite to said first active material.
 2. The method according to claim 1, wherein said first electrode is arranged to said first side by pressing the first powder directly onto the first side of the biplate, and/or said second electrode is arranged to said carrier by pressing the second powder directly onto the carrier.
 3. The method according to claim 1, wherein said first electrode and/or said second electrode is/are separately formed before being arranged to said biplate assembly, each electrode preferably including a mesh to serve as a support means.
 4. The method according claim 3, wherein said mesh is selected to be a polymer mesh, preferably an extremely fine polymer mesh.
 5. The method according to claim 1, wherein said carrier is selected to be a second side of the biplate, being opposite to said first side, and where said first type of active material is a positive active material and said second type of material is a negative active material.
 6. The method according to claim 1, wherein said biplate assembly further comprises a separator, said method further comprises the steps: adding the separator on top of the first electrode so that a first side of the separator covers the whole area of the first electrode, and the carrier is selected to be a second side of the separator, being opposite to the first side of the separator, and said first type of active material is a positive active material and said second type of material is a negative active material.
 7. The method according to claim 1, wherein said method further comprises the step: selecting a limited area on each side of the biplate where said first and second electrodes are to be in physical contact.
 8. The method according to claim 1, wherein said method comprises the step: treating the surface on each side of the biplate so as to obtain a three-dimensional roughness, thereby increasing the surface where each electrode is in physical contact.
 9. The method according to claim 8, wherein said three-dimensional roughness is achieved by flame spraying at least the selected limited areas with a similar material making up the biplate.
 10. The method according to claim 9, wherein the biplate is selected to be a Nickel plate and said flame spraying is performed by a Nickel material.
 11. The method according to claim 8, wherein said three-dimensional roughness is achieved by etching away material from the biplate in at least the selected limited areas.
 12. The method according to claim 8, wherein the step of treating the surface is restricted to the selected limited areas on each side of the biplate, where said first and second electrodes are to be in physical contact.
 13. The method according to claim 1, wherein said first powder is a nickel compound, including nickel fibres to establish better contact between the biplate and the first electrode.
 14. The method according to claim 1, wherein said second powder is a metal hydride compound, including fibres to establish better contact between the biplate and the second electrode.
 15. A biplate assembly including a biplate, a first electrode and a second electrode, said first electrode, which is formed by a compressed first powder, is in direct physical contact with a first side of the biplate, and the second electrode, which is formed by a compressed second powder, is arranged to a carrier arranged within said biplate assembly.
 16. The biplate assembly according to claim 15, wherein said first electrode is arranged to said first side by pressing the first powder directly onto the first side of the biplate, and/or said second electrode is arranged to said second side by pressing the second powder directly onto the carrier.
 17. The biplate assembly according to claim 15, wherein said first electrode and/or said second electrode is/are separately formed before being arranged to said biplate assembly, each electrode preferably including a mesh to serve as a support means.
 18. The biplate assembly according claim 17, wherein said mesh is a polymer mesh, preferably an extremely fine polymer mesh.
 19. The biplate assembly according to claim 15, wherein said carrier is a second side of the biplate, being opposite to said first side, and where said first type of active material is a positive active material and said second type of material is a negative active material.
 20. The biplate assembly according to claim 15, wherein said biplate assembly further comprises a separator arranged on top of the first electrode so that a first side of the separator covers the whole area of the first electrode, and the carrier is a second side of the separator, upon which the second electrode is arranged, said second side of the separator being opposite to the first side of the separator, and said first type of active material is a positive active material and said second type of material is a negative active material.
 21. The biplate assembly according to claim 15, wherein a limited area on each side of the biplate is in physical contact.
 22. The biplate assembly according to claim 15, wherein at least the surface of the biplate where the electrodes are to be in physical contact is treated to obtain a three-dimensional roughness.
 23. The biplate assembly according to claim 15, wherein the first powder is a nickel compound including nickel fibres to establish better contact between the biplate and the first electrode.
 24. The biplate assembly according to claim 15, wherein said second powder is a metal hydride compound including metal fibres to establish better contact between the biplate and the second electrode.
 25. A bipolar battery comprising a housing, a negative end terminal having a negative electrode, a positive end terminal having a positive electrode, at least one biplate assembly, each having both a negative and a positive electrode, which are formed by a compressed first and second powder, respectively, arranged to a biplate, arranged between said negative and positive end terminals in a sandwich structure and a separator is arranged between each adjacent positive and negative electrode.
 26. The bipolar battery according to claim 25, wherein said positive and/or said negative electrode is/are arranged to the biplate by pressing the first and second powder, respectively, directly onto respective side of the biplate.
 27. The battery according to claim 25, wherein said positive and/or said second negative electrode is/are separately formed before being arranged to said biplate assembly, each electrode preferably including a mesh to serve as a support means.
 28. The battery according to claim 27, wherein said mesh is a polymer mesh, preferably an extremely fine polymer mesh.
 29. A bipolar battery comprising a housing, a first end terminal, at least one biplate assembly, each having a first electrode, a separator and a second electrode mounted on a biplate in a sandwiched structure, each electrode are formed by a compressed first and second powder, respectively, said biplate operating as a second end terminal and said first electrode is arranged to be in physical contact with said first end terminal by pressing said first end terminal toward said biplate assembly.
 30. The bipolar battery according to claim 29, wherein said first is arranged to the biplate by pressing the first powder directly onto a first side of the biplate and/or said second electrode is arranged to the separator by pressing the second powder directly onto the separator.
 31. The battery according to claim 29, wherein said positive and/or said second negative electrode is/are separately formed before being arranged to said biplate assembly, each electrode preferably including a mesh to serve as a support means.
 32. The battery according to claim 31, wherein said mesh is a polymer mesh, preferably an extremely fine polymer mesh. 